North Polar Vortex Edge Animations

North Winter Polar Vortex Animations

This analysis uses the vortex edge selection developed by V. Lynn Harvey, R. Bradley Pierce, and Duncan Fairlie (A climatology of stratospheric polar vorticies and anticyclones, JGR 107 No. D20, 4432, doi:1029/2001jd001471,2002 ) which picks streamline(s) where the integrated value of "Q" (see paper for definition) changes sign.
The stream function program was contributed by William Randel (written/ modified by M. Fischer,1985 and Tom Blackshear,1990). The analysis is performed on global potential-temperature-level U,V grids. The data used are the daily stratospheric analyses from UK Met office ("UKMO", now "MetO") originally by way of the British Atmospheric Data Centre (BADC), now from The Centre for Environmental Analysis, CEDA. The more recent (after March 2006) high spatial resolution data are reduced, by selection, to the original 96 longitudes x 72 latitudes before analysis.
In the animations, cyclonic edges are solid, anti-cyclonic dashed. The average speed for cyclonic streamlines are written over their respective colours in the legend. If there is more than one line selected at a particular level, usually the speed label is for the larger ( but no guarantees). Sometimes there are nested edges at the same level - this remains a puzzle - but considering the noisiness of "Q", the integrated value is also sometimes noisy about zero, so more than one line can be selected.
Vortex edge analysis details

Another vortex edge method is by scaled PV (Gloria Manney), innner and outer edge defined by sPV levels, yellow filled: Example:Q method vs sPV(Manney) , and one rare case in very disturbed conditions where edge definition is a lost cause:Chaos

And just for pretty - here is a plot of streamlines with local speed indicated by colour. View Local Speeds

Winter 1991/92 Winter 1992/93 Winter 1993/94 Winter 1994/95 Winter 1995/96 Winter 1996/97 Winter 1997/98 Winter 1998/99 Winter 1999/00
Winter 2000/01 Winter 2001/02 Winter 2002/03 Winter 2003/04 Winter 2004/05 Winter 2005/06 Winter 2006/07 Winter 2007/08 Winter 2008/09
Winter 2009/10 Winter 2010/11 Winter 2011/12 Winter 2012/13 Winter 2013/14 Winter 2014/15 Winter 2015/16 Winter 2016/17 Winter 2017/18

Most recent winter day

Finally, here is a workshop paper on long term statistics

(Our go-to program for controlled viewing of the gif89a animations is "gif movie gear")